1. Field of the Invention
The present invention relates to a novel method of treatment of a fluid such as water or a gas containing a volatile organic halogenated compound. More particularly, it relates to a practically advantageous method of treating such a fluid with a reducing agent in the presence of a catalyst, thereby decomposing the volatile organic halogenated compound contained in and rendering the fluid ecologically harmless.
2. Description of the Prior Art
Volatile organic halogenated compounds must be removed from a ground and waste waters and from soil because they cause environmental pollution. Various methods have been examined for the treatment of service and waste waters containing volatile organic halogenated compounds. Examples of such methods are; (1) aeration treatment, (2) adsorption treatment, (3) decomposition treatment by oxidation, (4) biological treatment and (5) thermal decomposition. However, these methods have various problems and are not satisfactory.
For example, method (1) simply transfers the organic halogenated compounds from the underground water or soil to the atmosphere and does not bring a fundamental solution to the environmental problem. Method (2) can catch or recover the organic halogenated compounds and is applied in combination with the method (1) in many cases. This method has a problem in that the adsorption capacity of the adsorbent, such as an activated charcoal, is inevitably decreased by the influence of moisture. The method of adsorption has another problem that the adsorbent must be regenerated. When it is regenerated using steam, a waste water containing a high concentration of the organic halogenated compounds is discharged.
For the fundamental solution of the environmental pollution, a degradation method of the organis halogenated compounds, such as the methods (3) to (5), is required. The method of decomposition by oxidation (3) has been actively examined for the decomposition of the halogen compounds. Many reports can be found on the methods utilizing ultraviolet light, ozone, hydrogen peroxide and the like. Fewer reports are also found on the decomposition by methods (4) and (5).
In the methods of decomposition by oxidation and thermal decomposition described above, a large amount of energy is required for generation of ultraviolet light and ozone or for heating. Thus, these methods have problems that they inevitably lead to a higher cost of treatment and that organic halogenated compounds may be newly generated because the halogen formed by the decomposition reaction easily reacts with organic compounds present in the environment. The biological decomposition method (4) requires less amount of energy for the treatment but microbiological system which can efficiently decompose the organic halogenated compounds has not been discovered. Thus, biological decomposition is not practical either. A method of decomposition by reduction utilizing iron powder as a reducing agent was reported but this method is not yet practical either.